Liposomes for protection against toxic compounds

ABSTRACT

Methods of preparing a proteoliposome comprise the step of contacting a liposome with an effective portion of RalBP1 to create a proteoliposome. RalBP1 is effective for the protection and treatment of mammals and the environment against the accumulation of toxic compounds and prevents accumulation of one or more toxic compounds, reduces the concentration of toxic compounds, and protects against further contamination with one or more toxic compounds.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/912,788, filed Jun. 7, 2013, pending, which is a divisionalapplication of U.S. patent application Ser. No. 11/741,447, filed Apr.27, 2007, issued on Jul. 16, 2013, as U.S. Pat. No. 8,486,410, which isa divisional application of U.S. patent application Ser. No. 10/713,578filed Nov. 13, 2003, now abandoned, which claims the benefit of U.S.Provisional Patent Application No. 60/425,814, filed Nov. 13, 2002.These applications are incorporated by reference herein in theirentireties.

STATEMENT AS TO TIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT

This invention was made with government support under CA 77495 awardedby the National Institutes of Health. The government has certain rightsin this invention.

REFERENCE TO A SEQUENCE LISTING

This application incorporates by reference sequence listing materialincluded on computer readable form and identified asTER_(—)001US5_Sequence_Listing ST25.txt saved on Dec. 3, 2014, in ASCIIreadable form.

BACKGROUND OF THE INVENTION

The present invention relates to the bioremediation (e.g., removal) oftoxic compounds, and more specifically to the protection of mammals andthe environment against toxic organic compounds, their related speciesand metabolites, especially those that result from damage or stress.

Toxic compounds can harm both humans and the environment. Toxiccompounds are often referred to as xenobiotics. These compounds aregenerally highly toxic to life forms (including humans), are exceedinglydifficult to dispose of, and are of major concern to industry (becauseof the cost and/or difficulty of treatment) and to regulatory agencies.Toxic compounds may be by-products of larger molecules, or may resultfrom damage to biological molecules (e.g., stress that is drug-induced,chemically-induced, or physiologically induced). The damage may also bephysiologic in nature (e.g., the result of an oxidative or alkylatingnature) or be produced by radiation.

In the environment, a large source of xenobiotics arises from themanufacturing of chemicals (e.g., benzene, toluene, styrene, pesticides,dioxins, halogenated organic compounds such as pentachlorophenol andPCB, and polybrominated diphenyl ethers). Toxic environmental pollutantsare often present in process waste streams, and may be present in largerquantities after spills, or in the soil and water associated withabandoned or poorly controlled industrial sites.

Environmental toxic compounds, whether in process waste streams or inspills, are now generally treated by physical, chemical or biologicalmeans. One means includes trying to physically remove the toxicmaterials, e.g., from air and water streams, by contacting the toxinswith activated carbon particles contained within adsorption columns. Asignificant drawback of this approach is that the xenobiotics adsorbedonto the carbon are not destroyed, only physically removed from thecontaminated stream, and therefore some subsequent disposal method todestroy the toxins must still be employed. Toxic organic compounds mayalso be removed by chemical means (e.g., incineration); however, thisapproach is costly (e.g., high temperature and pressure equipment arerequired) and results in the release of undesirable combustion productsinto the atmosphere. Therefore, there remains a need to cost-effectivelyprocess environmental toxic organic compounds without addingenvironmental insults or wastes into the surroundings.

Biological treatment of toxic compounds often involves the addition ofthe toxic material to bioreactors (i.e., tanks with aqueousmicroorganism suspensions) to degrade the materials to harmless endproducts such as carbon dioxide and water. Although potentially thelowest cost approach to xenobiotic destruction, current biologicaltreatment of toxic organics suffers from fundamental inefficiencies. Forexample, the toxic material often kills the microorganisms (this isespecially common with conventional wastewater treatment systems).Another drawback is that when added too slowly, microorganisms presentin a biotreatment system often starve or become unable to consume thetoxic compounds. Because of the above problems with currentbioremediation there still remains a long-felt need to transform thesetoxic compounds in a more efficient, controlled, and cost-effectivemanner.

In mammals, toxic compounds may arise from environmental contact, fromingestion or infusion of organic or inorganic chemicals (includingpharmaceutical and herbal products), and from internal oxidative damageor stress, alkylating damage, or radiation damage. Environmentalcontaminants, poisons, allergy producing agents and chemicals (such aspesticide residues), toxic trace elements, certain drugs andpharmaceuticals, as well as excessive levels of other non-end productmetabolites that are formed in biochemical reactions in the body duringstates of altered metabolism are examples of compounds that may producetoxic organic compounds. Mammalian syndromes, conditions, and diseasesmay also lead to the accumulation of these toxic compounds, examples ofwhich include fatigue, cancer, hypotonia, depression, lassitude, muscleweakness, insomnia, recurring bad dreams, intestinal complaints(myalgia), confusion, and functional nervous system problems.

Most mammals contain intrinsic biotransformation-detoxification pathwaysto rid themselves of naturally occurring toxic organic compounds;however, these physiologic pathways are only efficient whenbiotransformation-detoxification requirements are small. Undersituations of stress (e.g., oxidative, alkylating, radiation) or whennormatural chemicals are introduced, naturalbiotransformation-detoxification pathways are, themselves, oftenincapable, inefficient and ineffective at ridding the cell or thebiologic system of the chemical. Often, the chemical may be initiallytransformed after which potentially toxic by-products then accumulatewithin the host and can prove fatal. Attempts to protect mammals fromtoxic accumulation of organic compounds and their by-products aregenerally done after chemical insult has already occurred. The additionof chemicals, foods, vitamins, nutritional supplements or drugs may beused to try to relieve the body of the excessive toxins. Most of theadditives, however, are either inefficient, costly and/or have seriousdeleterious side effects. For mammals, these current inefficiencies andproblems mean that there remains a need to aid in the protection ofmammals against toxic organic compounds in an efficient, controlled, andcost-effective manner.

SUMMARY OF THE INVENTION

The present invention solves the current problems associated withremoval of toxic wastes (e.g., toxic waste compounds, xenobiotics) fromthe environment, from biologic waste, and from mammals. As identifiedherein is a novel protein that is a non-ABC transporter, referred toherein as RLIP76 and with an official human genome name of ralA bindingprotein also referred to herein as RalBP1, that efficiently detoxifiesxenobiotics by a process that catalyzes ATP. Importantly, the protein isuseful in the protection of mammals against xenobiotic accumulation andfor the transport of xenobiotic waste in the environment oftenassociated with industrial and chemical processing. RalBP1 is alsoidentified as a protein involved in drug resistance and in theprotection against toxic by-products of metabolism, stress, and drugs orother organic chemicals.

Generally, and in one form, described herein is a method of preparing aproteoliposome comprising the step of contacting a liposome with aneffective portion of RalBP1 to create a proteoliposome. The liposome isgenerally selected at least from the group consisting of lectin,glycolipid, phospholipid, and combinations thereof. In another aspect,the proteoliposome is added to one or more toxic compounds to reduce theconcentration of toxic compounds, prevent the accumulation of toxiccompounds, and protect against further contamination with one or moretoxic compounds. Toxic compounds may be present in an organism,mammalian cell, transfected mammalian cell, bioreactor, soil, water,spill, process waste stream, manufacturing waste chemical waste,laboratory waste, hospital waste, and combinations thereof, to which theproteoliposome is then added.

In another form, described herein is a proteoliposomal compositioncomprising a liposome and an effective portion of RalBP1. Theproteoliposome is used to reduce the concentration of toxic compoundsand may further comprise at least 4-hydroxynonenal, leukotriene,polychlorinated biphenyls, glutathione, and combinations thereof. Theeffective portion of RalBP1 is dependent on ATP for optimal activity. Asdiscussed, the proteoliposomal composition is generally used for thetreatment of toxic compound exposure, is capable of being transfectedinto a mammalian cell, and is capable of having antibodies generatedagainst it. The composition may be applied or administered to anorganism in need thereof by injection, dermal delivery, infusion,ingestion, and combinations thereof and capable of producing the desiredeffects.

In yet another form, described herein is a method of reducing theeffects of ionizing radiation comprising the step of adding aproteoliposome to a material with ionizing radiation, wherein theproteoliposome is a liposome and an effective portion of RalBP1.Alternatively, the proteoliposome may be added before the ionizingradiation. Ionizing radiation may include x-ray radiation, gammaradiation, ultraviolet radiation, thermal radiation, nuclear radiation,and combinations thereof.

Another embodiment is a kit prepared for using the proteoliposomalcomposition described above comprising an effective dose of aproteoliposome, wherein the proteoliposome is a liposome and aneffective portion of RalBP1 and an instructional pamphlet. The kit isgenerally used to reduce the concentration of toxic compounds and theirby-products and to enhance resistance to toxic compounds.

The benefits of RalBP1 include the environmental, chemical and biologicprotection against toxic compound and xenobiotic. RalBP1 is critical inthe transport of toxic compounds and xenobiotics and for enhancingresistance to drugs/chemicals and their toxic by-products (e.g.,chemotherapy and radiation therapy). As used herein, toxic compoundsarise as by-products of chemical and manufacturing processes (e.g.,waste products), metabolism, pathologic conditions, stress, radiation,and drugs/chemicals, as examples.

Those skilled in the art will further appreciate the above-notedfeatures and advantages of the invention together with other importantaspects thereof upon reading the detailed description that follows inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures, wherein:

FIG. 1 is a schematic representation of the pathway of detoxificationmechanisms of xeno- and endobiotics showing the role of a transportersuch as RalBP1;

FIG. 2 depicts human RalBP1 cDNA nucleotide sequence (SEQ ID NO:1),deduced amino acid sequence (SEQ ID NO:2) and peptide characterization;

FIG. 3 depicts the effect of heat shock and H₂O₂ exposure on GS-HNEtransport in K562 cells;

FIGS. 4A and 4B depict the effect of heat shock on the H₂O₂ mediatedcytotoxicity in K562 cells (FIG. 4A) and the protective effect of heatshock and H₂O₂ pre-treatment on H₂O₂ induced apoptosis in K562 cells(FIG. 4B);

FIG. 5 depicts the effect of anti-RalBP1 IgG on 4-HNE mediated apoptosisin heat shock pre-conditioned cells;

FIG. 6 depicts the effect of RalBP1 on radiation sensitivity, whereinthe mean and standard deviation of values from three groups shown are:without treatment with liposomes (circle), treatment with liposomeswithout RalBP1 (square), and treatment with liposomes with RalBP1(triangle); and

FIG. 7 depicts examples of the physiological significance of RalBP1. Allfigures are in accordance with at least one aspect of the presentinvention;

FIGS. 8A, 8B, 8C, and 8D depict the knockout and genotyping strategy asembodied in one aspect of the present invention, the insertion sitesequence (SEQ ID NO:3) and the third LTR primer sequence (SEQ ID NO:4)are shown.

FIGS. 9A, 9B, 9C, and 9D depict the effect of RIP1 on radiationsensitivity in male C57 mouse as embodied in one aspect of the presentinvention;

FIGS. 10A, 10B, and 10C depict the effect of RIP1 knockout, radiationand gender on DOX and DNP-SG transport as embodied in one aspect of thepresent invention;

FIG. 11 depicts tissue-specific effects of RIP1 knockout on parametersreflecting oxidative stress in un-irradiated animals;

FIG. 12 depicts tissue-specific effects of RIP1 knockout on parametersreflecting oxidative stress in X-irradiated animals; and

FIG. 13 depicts sample results of one way, two way and three wayinteractions of gender, genotype and radiation by ANOVA.

DETAILED DESCRIPTION OF THE INVENTION

Although making and using various embodiments of the present inventionare discussed in detail below, it should be appreciated that the presentinvention provides many inventive concepts that may be embodied in awide variety of contexts. The specific aspects and embodiments discussedherein are merely illustrative of ways to make and use the invention,and do not limit the scope of the invention.

In the description which follows like parts may be marked throughout thespecification and drawing with the same reference numerals,respectively. The drawing figures are not necessarily to scale andcertain features may be shown exaggerated in scale or in somewhatgeneralized or schematic form in the interest of clarity andconciseness.

As used herein, a “proteoliposome” is generally a protein and lectin orglyco- or phospholipid combination that forms a sphericalmicellular-like or vesicular structure. The structures may formspontaneously or by chemical or mechanical manipulation, or combinationsthereof. Proteoliposomes take advantage of the amphipathic nature of thelipid (or lectin) that causes them to form bilayers when in solutionresulting in at least one of several shapes, including: (a) sphericalmicelle with the tails inward, or (b) bimolecular sheets that arebilayers with hydrophobic tails sandwiched between hydrophilic headgroups. In general proteoliposomes may reseal themselves when torn orbroken. Proteoliposomes may contain only one lectin or lipid or avariety and combination of each. Examples of phospholipids includephosphatidylcholine, sphingomyelin, phosphatidylserine, inositolphospholipids, and phosphatidylethanolamine. When used, proteoliposomesmay be charged or electrically neutral and are generally used atphysiological pH. They may also be structures mixed with detergent(e.g., detergent/lipid/protein, detergent/lectin/protein). Methods forpreparing proteoliposomes of defined lipid-protein or lectin-proteinratios and size are well-known to one of ordinary skill in the art ofmolecular biology and protein/lipid biochemistry.

“Toxic compounds” as used herein may xenobiotics, radiation, toxins,waste products, by-products of larger organic or inorganic moleculesand/or may result from damage to such molecules. Stress is one exampleof damage. Other damages may be environmentally-induced,metabolically-induced, drug-induced, chemically-induced,radiation-induced, and physiologically induced, as examples. The toxiccompounds may be in a mammal or occur in the environment or come frommanufacturing and/or chemical processes that produce waste products.Toxic compounds, “toxic organic chemicals,” and “xenobiotics” are oftenused interchangeably. Toxic compounds may also include crude oil, crudeoil fraction, an organic or inorganic chemical compound, radiation, achemical solvent, metabolite, metabolic by-product, a chemical warfareagent, drug, drug by-product, chemical by-product, and combinationsthereof.

As used herein, an “antibody” is an immunoglobulin, a solution ofidentical or heterogeneous immunoglobulins, or a mixture ofimmunoglobulins.

The term “protein,” as used herein, is meant to include any chain ofamino acids and includes peptides, polypeptides, proteins, recombinantproteins, and modified proteins, such as glycoproteins, lipoproteins,phosphoproteins, metalloproteins, and the like.

As used herein, “an effective portion of-RalBP1,” is any combination ofproteolytic peptide products of RalBP1 that, when combined, promotes thetransport or prevents the accumulation of toxic organic compounds and/orenhances resistance to the toxic compounds. The effective portion may bea recombinant RalBP1.

Any conventional eukaryotic or bacterial expression vectors, of whichmany are known in the art, may be used in the practice of this inventionto transfect mammalian cells or bacterial cells with the claimedproteoliposome. “Transfection” as used herein, may refer to theincorporation of a nucleic acid or protein into a cell by any meansreadily known in the art of molecular biology. As examples, transfectionmay include incorporation by proteoliposomes, electroporation, by viralincorporation, or by a nucleic acid-containing structures (e.g.,expression vector or plasmid) and combinations thereof. The eukaryoticcell expression vectors described herein may be synthesized bytechniques well known to those skilled in this art. The components ofthe vectors such as the bacterial replicons, selection genes, enhancers,promoters, and the like may be obtained from natural sources orsynthesized by known procedures. Expression vectors useful in practicingthis invention may also contain inducible promoters or compriseinducible expression systems as are well known in the art. Theexpression vectors may be introduced into the host cells by purelyconventional methods, of which several are known in the art.

The terms “mammal” or “mammalian” and “organism” are often usedinterchangeably throughout the discussion of the present invention.

All technical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which thisinvention belongs, unless defined otherwise. All publications mentionedherein are incorporated herein by reference to disclose and describe themethods and/or materials in connection with which the publications arecited.

Bioremediation

The bioremediation or removal of toxic compounds or xenobiotics inmammals is traditionally classified into two phases—Phase I and PhaseII—and the detoxification process is often classified as Phase III.Phase I reactions are those catalyzed by enzymes including cytochromeP450, epoxide hydrolases, esterases, and amidases. These enzymesintroduce/expose reactive groups in xenobiotics that create bioactivatedmetabolites that can then be conjugated to hydrophilic compounds, suchas glutathione (GSH), glucuronate, sulfate, etc., by Phase II enzymes.Phase II reaction products must eventually be transported to completethe detoxification process (Phase III) because accumulation of theseproducts can cause not only toxicity but can inhibit Phase II reactions.Hence, transport mechanisms designated as Phase III are an essentialcomponent of mammalian cellular defense mechanisms against toxicchemicals or xenobiotics (shown schematically in FIG. 1).

Both Phase I and Phase II biotransformation enzymes occur as members ofmultiple gene “superfamilies” that have been extensively characterized(e.g., CYP450s and glutathione S-transferases). In contrast, relativelylittle is known about the transporters comprising Phase III of thedetoxification process. Some of the transporters may belong to severalsuperfamilies or a small family specific to eukaryotic organisms;however, these molecules are not well understood physiologically orfunctionally. Known transporters are ABC transporters particularlyP-glycoprotein (Pgp) and the multidrug resistance associated protein(MRP1). Little is understood about any other molecules that comprise thePhase III enzymes involved in the detoxification process.

The present invention has identified a non-ABC transporter, RalBP1, as anovel protein that efficiently detoxifies xenobiotics. While the proteinhas reported GTPase activity, the present invention discloses thatRalBP1 is involved in the catalysis ATP. As presented herein, RalBP1catalyzes ATP-dependent uphill transport of xenobiotics and theirby-products. Its activity is stimulated by chemotherapeutic agents andis found to have two ATP-binding sequences that, when mutated, abrogatethe ATP-binding, ATPase activity and transport function of the protein.RalBP1 may be reconstituted in proteoliposomes and mediatesATP-dependent saturable transport of xenobiotics and their by-products.Furthermore, transfection of the RalBP1 protein into mammalian cellsconfers resistance to chemotherapeutic agents. Cells enriched withRalBP1 also acquire resistance to xenobiotic toxicity. In addition,RalBP1 catalyzes the transport of physiologic ligands such asleukotrienes (LTC4) and the conjugate of 4-hydroxynonenal (4-HNE) andglutathione.

Transporters of the ABC Family

ABC transporters utilize the free energy of ATP hydrolysis totranslocate substrates or allocrites across the membrane, and haveWalker motifs (ATP binding sites) and transmembrane domains in theirsequences. Overexpression of ABC transporters has been linked with drugresistance of certain bacteria, parasites and human cancer cells. TwoABC transporter family members P-glycoprotein (Pgp or MDR1) andmultidrug resistance associated protein (MRP1) are characterized withrespect to this function. Overexpression of Pgp, MRP1, or both isobserved in many cancer cell lines exhibiting the multidrug resistancephenotype. Pgp overexpressing cancer cells exposed to a drug such as achemotherapeutic agent (e.g., adriamycin, vinblastine, colchicines) showdecreased accumulation of the drug.

MRP, now designated as MRP1 (first characterized member of the MRPfamily) or ABCC1 was originally cloned from a drug resistant lineselected for doxorubicin (DOX) resistance. MRP1-mediated transport ofthe conjugates of GSH, glucuronate, and sulfate has been clearlydemonstrated. MRP 1 also mediates the transport of physiologicalGSH-conjugates (e.g., leukotrienes, GS-HNE-GSH conjugate of lipidperoxidation end product, 4-HNE). Transport of vincristine by MRP1-richmembrane vesicles has been demonstrated and this transport has beensuggested to be linked to GSH co-transport.

Despite the identification of multiple families of drug transporters inthe human genome, including at least 48 sequences of putative proteinshaving characteristics of ABC-transporters, the functionalcharacterization of these transporters is lacking.

The present invention describes the function of a protein, not of theABC transporter family, that has a novel role as a primary activetransporter of xenobiotics, their conjugates, toxic metabolicby-products (including drug- or physiologically induced), and otherchemicals (e.g., chemotherapeutic agents), especially those involved indrug resistance. The novel protein of the present invention functions asa Ral-binding, GTPase-activating protein or RalBP1. RalBP1 functionresults in transport of molecules associated with drug resistance and ofexogenous and endogenous toxicants.

DNP-SG ATPase: A Transporter for Anionic and Cationic Xenobiotics

DNP-SG ATPase is a protein in membranes of human cells that catalyzesATP hydrolysis in the presence of GSH-conjugates. It was so namedbecause S-(2,4-dinitrophenyl)glutathione (DNP-SG) stimulated its ATPaseactivity. The presence of DNP-SG ATPase was demonstrated in all humantissues examined including liver, heart, lung, muscle, kidneys,erythrocytes, leukocytes and various human cell lines of diverse tissueorigin. [See LaBelle E F, et al. 1988. FEBS Lett 228:53-6; Sharma R, etal. 1990. Biochem Biophys Res Commun 171:155-61; Saxena M, et al. 1992.Arch Biochem Biophys 298:231-7; Awasthi S, et al. 1994. J Clin Invest93:958-65; Awasthi S, et al. 1998. Biochemistry 37:5231-8; Awasthi S, etal. 1998. Biochemistry 37:5239-48; all citations incorporated herein byreference.] DNP-SG ATPase-mediated ATP hydrolysis was stimulated notonly by organic anions (e.g., DNP-SG), but by cations such aschemotherapeutic agents (e.g., doxorubicin or DOX) and theirmetabolites. DNP-SG ATPase catalyzed transport of anionic GSH conjugatesas well as of weakly cationic drugs such as DOX and colchicine (Awasthiet al. 1994, 1998a, 1998b, 1999, incorporated herein by reference).

ATP-dependent transport of both anions and cations against aconcentration gradient was demonstrated in proteoliposomes reconstitutedwith highly purified DNP-SG ATPase. Transport was temperature-dependentand sensitive to the osmolarity of the assay medium. ATP hydrolysis wasrequired for the transport because when ATP was replaced by itsnon-hydrolyzable analogue, methylene-adenosine triphosphate (Met-ATP),transport activity was abolished. This suggested that transport wasdirectly coupled to ATP hydrolysis, and that DNP-SG ATPase was a primaryactive transporter. Antibodies raised against DNP-SG ATPase inhibitedthe transport of anions and cations in inside-out vesicles (IOVs)prepared from erythrocyte membranes suggesting that the transport wasspecifically catalyzed by DNP-SG ATPase. On the other hand, antibodiesagainst MRP1 or Pgp neither recognized DNP-SG ATPase in Western blotsnor affected its transport activity, establishing that DNP-SG ATPase wasa distinct transporter.

A protein related to DNP-SG ATPase was also identified in rodents(Zimniak P, et al. 1992. Arch Biochem Biophys 292:534-8; Zimniak P,Awasthi Y C. 1993. Hepatology 17:330-9; Pikula S, et al. 1994. J BiolChem 269:27574-9; Pikula S, et al. 1994. J Biol Chem 269:27566-73; allcitations herein incorporated by reference). Antibodies against humanDNP-SG ATPase recognized the protein in rat canalicular membranes. Whenpurified and reconstituted in proteoliposomes, it catalyzedconcentrative transport of DNP-SG with kinetic parameters similar tothose of human DNP-SG ATPase. The biochemical characteristics of the rattransporter and human DNP-SG ATPase were clearly distinct from the MRP2from human and rats. These results clearly demonstrate that in mammals,other transporter(s) besides MRP2 is/are present.

Cloning of DNP-SG ATPase and its Identity with RalBP1

The molecular identity of DNP-SG ATPase remained elusive for over adecade because of the inherent difficulties in its purification (e.g.,protein was prone to degradation, and peptides of varying chain lengthswere observed in SDS gels of purified preparations, especially a 38 kDapeptide fragment). Purified preparations highly enriched in the 38 kDapeptide were found to mediate ATP-dependent, uphill transport of anionsand cations in reconstituted proteoliposomes.

Immunoscreening of a human bone marrow cDNA library using polyclonalantibodies against the 38 kDa DNP-SG ATPase peptide yielded RalBP1(Awasthi S, et al. 2000. Biochemistry 39:9327-34, herein incorporated byreference). At this time RLIP was thought of as a Ral binding,GTPase-activating protein (GAP), and to bridge the Ral, Rac, Cdc42pathways.

The present invention now describes the expression of RalBP1 in E. colithat shows the recombinant protein readily undergoes degradation,yielding peptide fragments in SDS gel dependent on the conditions ofpurification, including a 95 kDa band and 38 kDa fragment. All thefragments are recognized by antibodies raised against DNP-SG ATPase andhave internal sequences of RalBP1 (FIG. 2), demonstrating that thesefragments originate from RalBP1 and result from proteolytic processing.Primary fragments are the C-RalBP1⁴¹⁰⁻⁶⁵⁴ and N-RalBP1¹⁻³⁶⁷ derived fromthe C- and N-terminus of RalBP1, respectively (Awasthi S, et al. 2001.Biochemistry 40:4159-68, herein incorporated by reference).

For FIG. 2, human bone marrow cDNA lambda gtl 1 expression library wasscreened with antibody against human DNP-SG ATPase, the positive plaqueswere purified and the recombinant Lambda DNA were sequenced and sequencecomparisons with published sequences were generated by the Blast Programavailable as a network service from the National Center forBiotechnology Information, NIH, such that the results showed the DNAsequence from the positive plaque was the same as the human RalBP1protein mRNA coding sequence. The encoding sequence of RalBP1 wassubcloned into prokaryotic expression vector pET30 and the recombinantRalBP1 was purified and sequenced and the deduced amino acid sequencewas analyzed with the help of the Wisconsin Genetics Computer Group withdifferent sequence identifications that include experimentallydetermined sequences of RalBP1 peptides obtained during purification(e.g., Leucine zipper pattern, N-myristoylation site, Trypsin cut site,Chymotrypsin site, Protein kinase C phosphorylation site, Tyrosinekinase phosphorylation site, N-Glycosylation site; cAMP-dependentprotein kinase site, cGMP-dependent protein kinase site, and Caseinkinase II phosphorylation site).

RalBP1 Mediates ATP-Dependent Transport of Organic Anions and Cations

DNP-SG ATPase and RalBP1 may be, in many species, the same protein.Hence, recombinant RalBP1 (rec-RalBP1) shows constitutive ATPaseactivity stimulated by anionic (e.g., DNP-SG) and cationic (e.g., DOX)ligands with similar Km. Purified rec-RalBP1 reconstituted inproteoliposome (e.g., with asolectin or phospholipids of definedcomposition) catalyzes ATP dependent, uphill transport of anionicconjugates (e.g., DNP-SG, GS-HNE) and cationic amphiphilic drugs (e.g.,DOX and daunomycin) such as those used in cancer chemotherapy. Theresults show that the mechanism through which RalBP1 transports chargedchemicals (e.g., anthracyclines, vincristine) is distinct from that ofMRP1. RalBP1 is not selective, it transposes both anions as well ascations. More importantly, the transport does not require GSHco-transport.

TABLE 1 summarizes structural characteristics, chromosomal location,tissue localization and substrate profiles of RalBP1, MRP1 and Pgp. TheTABLE shows that RalBP1 does not share structural attributes with MRP1or Pgp.

TABLE 1 Comparison of the characteristics of RLIP76 with Pgp (MDR1) andMRP1 RalBP1 MDR1 (Pgp) MRP1 Mol. Weight 76 kDa 170 kDa 190 kDaChromosomal Chromosome 18 Chromosome 7 Chromosome 16 Location TopologyNo clearly defined 2 TMDs and 2 NBDs 2 TMDs similar to Pgp TMDs. One NBDeach with Walker A and B with an extra TMD0 in the N and C-terminalmotifs. connected with L0 loop. domains are distinct 2 NBDs with WalkerA from Walker A and B and B motifs. motifs. Expression in Ubiquitouslyexpressed Widely expressed in Widely expressed in human tissues inmammalian tissue: human tissue: liver, human tissue: epithelia,erythrocytes, liver, kidney, brain, pancreas, muscle cells and lung,bone, muscle, colon adrenal gland, macrophages. kidney, and from smallintestine. cultured cells of mammalian origin. Localization in Plasmamembrane, Apical surface of Cytoplasmic or human tissues nuclearmembrane and epithelia (normal unidentified vesicular cytoplasm.tissue); plasma fraction (normal); membrane (malignant plasma membranecells). (malignant cells). Transport Cations and anions;Vinca-alkaloids, GSH-conjugates, allocrites GSH-conjugates,anthracyclins, taxanes glucuronides, bile salts; (example ofglucuronides, vinca- GSH not required for GSH co-transport substrates)alkaloids, co-transport. required for anthracyclins; GSH notvinca-alkaloids, required for co- anthracyclins. transport.Abbreviations: TMD = trans membrane domain; NBD = nucleotide bindingdomain.

As described herein, physiologic significance of the ATP-dependenttransport of both anions and cations by RalBP1 was confirmed bytransfection experiments. Cells overexpressing RalBP1 show increasedefflux of anions and cations (e.g., DOX, GS-HNE, leukotrienes) andacquired resistance to both DOX and 4-HNE induced cytotoxicity.

The transport of DOX is demonstrated in crude erythrocyte membranevesicles. Addition of purified protein to crude erythrocyte membranevesicles resulted in increased ATP-dependent DOX-transport in thesevesicles in a manner linearly dependent on the amount of purifiedprotein added. In these vesicles, DOX transport was competitivelyinhibited by anionic metabolites GS-E (DNP-SG), and bilirubin-ditaurate,as well as cationic drugs including anthracyclines (e.g., daunorubicin,mitoxantrone), vinca alkaloids (e.g., vinblastine), and calcium channelinhibitors (e.g., verapamil). (See TABLE 2)

TABLE 2 Stimulation of human erythrocyte DNP-SG ATPase (RalBP1)activities Stimulator/Allocrite Fold Activation K_(M) (μM) LeukotrieneC4 2.7 5.3 Leukotriene D4 1.9 7.7 Leukotriene E4 2.0 10 N-acetylLeukotriene E4 2.1 2.6 Adriamycin 2.3 2.8 Dihydroadriamycin 1.9 2Adriamycinone 2.2 5.8 Dihydroadriamycinone 2.4 5.2 Deoxyadriamycinone2.1 7.6 S-(methyl)-glutathione 1.4 137 S-(n-propyl) glutathione 1.5 —S-(n-pentyl) glutathione 1.6 — S-(n-decyl) glutathione 1.7 1528S-(p-chlorophenacyl) glutathione 1.8 — S-(9,10-epoxy stearyl)glutathione 1.9 674 S-(p-nitrobenzyl) glutathione 1.9 —S-(dinitrophenyl) glutathione 2.0 58

ATPase activity of purified protein fractions was then measured in theabsence and presence of several stimulators. Each assay was performedwith 9 replicates and about 2 μg protein was used for eachdetermination. Km values were obtained from double reciprocal plots ofstimulator vs. activity. For fold activations shown in TABLE 2, theconcentration of stimulator used was generally 2-fold the Km. TABLE 2explains the pharmacologic and toxicologic interactions between certaincationic drugs (e.g., natural product chemotherapy agents, calciumchannel blockers, immune suppressants) and electrophilic compounds/drugs(e.g., alkylating chemotherapy agents, endogenously generatedelectrophiles from lipid oxidation) that may be metabolized to theirby-products such as GS-E. This is particularly useful because some cells(e.g., erythrocytes) do not possess the full complement of metabolicmachinery to metabolize GS-E to mercapturic acids.

Structure of RalBP1

Primary structure of RalBP1 reveals several interesting features. Theprotein may be divided into four regions out of which two centraldomains carry a Rac1/CDC42 GAP activity and a Ral binding domain. Thefunction of two flanking domains are still unknown. The amino acidsequence of RalBP1 is depicted in FIG. 2 and indicates the presence ofsites for N-glycosylation (aa 341-344), cAMP (aa 113-116),cGMP-dependent protein kinase phosphorylation (aa 650-653), tyrosinekinase phosphorylation (aa 308-315), N-mysristolation (aa 21-26, aa40-45, aa 191-196), leucine zipper pattern (aa 547-578) and severalprotein kinase C phosphorylation, casein kinase II phosphorylation,trypsin and chemotrypsine cut sites. The presence of such motifs in theprimary structure of RalBP1, and its facile proteolytic degradationshows RalBP1 to be involved in several intra and extracellular processes(e.g., protein processing, intracellular signaling, protein degradation,recognition, tagging, etc.) and that proteolytic processing of RalBP1 isrequired for the multiple functions. The peptide fragments of RalBP1individually or in association with other fragments may catalyze thesevarious functions. For example, N-terminal and C-terminal fragments ofRalBP1, fragments that are individually incapable of mediatingATP-dependent transport, can catalyze the transport of electricallycharged drugs (e.g., DOX, colchicines) when reconstituted together inproteoliposomes.

RalBP1 Contains Two ATP-Binding Sites

RalBP1 expressed in cultured cells or in E. coli undergoes facileproteolysis during purification. Two most prominent peptides,N-RalBP1¹⁻³⁶⁷ and C-RalBP1⁴¹⁰⁻⁶⁵⁵, arising from the N- and C-termini ofRalBP1, respectively, appear as 49 kDa and 38 kDa in SDS-gels. Boththese peptides display constitutive ATPase activity that may bestimulated in the presence of the anionic or cationic ligandstransported by RalBP1. Both peptides bind ATP, as shown by photoaffinitylabeling that increased in the presence of vanadate, indicating thetrapping of a reaction intermediate in the ATP binding site (data notshown). None of the two fragments catalyze transport when reconstitutedalone in proteoliposomes. However, when reconstituted together,ATP-dependent transport of charged chemicals (e.g., DNP-SG, DOX) isobserved with kinetic parameters similar to those for RalBP1. The ATPbinding sites in N-RalBP1¹⁻³⁶⁷ and C-RalBP1⁴¹⁰⁻⁶⁵⁵ were identified to be⁶⁹GKKKGK⁷⁴ and ⁴¹⁸GGIKDLSK⁴²⁵, respectively. Mutations of K⁷⁴ and K⁴²⁵in the N- and C-terminal peptides, respectively, abrogate the ATPaseactivity, ATP binding capacity and transport function. The sequence ofthese ATP binding sites are not identical to the consensus sequence forthe P-loop (Walker motif).

Unlike the ABC transporters, no transmembrane alpha-helices are evidentin the RalBP1 sequence. Its association with membranes has, however,been demonstrated by immuno-histochemical studies using specificantibodies (Awasthi S, et al. 2002. Proceedings of the AmericanAssociation for Cancer Research, 43:Abst. 4717; herein incorporated byreference). The extraction of RalBP1 from cell lysates requiresdetergent, suggesting membrane association, a feature essential fortransport.

These findings show a greater diversity in this transporter, in terms ofstructural elements defining ATP binding and mode of membrane insertion,than is currently accepted. In addition, the distinction betweentransporters for anions as opposed to neutral or cationic substrates isblunted because RalBP1 catalyzes the transport of both, and, in contrastto MRP 1, does so without co-transporting GSH.

Another intriguing aspect of RalBP1 function is that it undergoes facileproteolytic fragmentation and many of the resulting peptides may bereconstituted into an active transport complex, a function that may helpregulate exocytosis and membrane ruffling (data not shown).

Toxic Compounds and Xenobiotic Protection with RalBP1

Physiologic stress or damage (e.g., mild transient heat shock oroxidative stress) induces RalBP1 activity and the activity is in advanceof inducing other heat shock proteins or the antioxidant enzymes, whichconstitute the typical stress response (Cheng J Z, et al., 2001. J BiolChem 276:41213-23, incorporated herein by reference). For example, whenK562 cells are exposed to a mild heat shock (about 42 degrees Centigradefor 30 minutes) or oxidative stress (about 50 μM H₂O₂ for 20 minutes)and allowed to recover for 2 hours, enhanced LPO is observed in stressedcells as compared to non-stressed cells. There is a 3-fold induction ofa GST isozyme, hGST5.8, that catalyzes the conjugation of 4-HNE and GSHto GS-HNE, and a 3.7-fold induction of RalBP1 that mediatesATP-dependent transport of GS-HNE from cells. As shown in FIG. 3, thecells preconditioned with stress transported GS-HNE at three-fold higherrate as compared to unstressed cells. This followed a greater than3-fold induction of RalBP1 in the preconditioned cells. For FIG. 3, K562cells (5×10⁷ cells) were exposed to 42 degrees Centigrade for 30minutes, and allowed to recover for 2 hours in medium at 37 degreesCentigrade. Cells were pelleted and re-incubated for 10 minutes at 37degrees Centigrade in 2 mL medium containing 20 μM [³H]-4-HNE, followedby pelleting and two washes with 2 mL of phosphate-buffered saline(PBS). The supernatants and washings were discarded and the cells wereincubated at 37 degrees Centigrade for 2 hours in 2 mL of 4-HNE freemedium after which radioactivity was determined in the medium. Thehemiacetal 3-(4-hydroxynonanyl) glutathione (inset, FIG. 2) was isolatedby HPLC and characterized by mass spectral analysis. For H₂O₂ treatmentthe cells were incubated for 20 minutes at 37 degrees Centigrade inmedia containing 50 μM H₂O₂ and after incubation, the cells werepelleted, washed free of H₂O₂, incubated in H₂O₂ free medium at 37degrees Centigrade for 2 hours and subsequently the radioactivity wasmeasured in the medium. For treatment with antibodies, the cells, afterheat shock treatment, were allowed to recover for 1 hour and respectiveIgGs were added (20 μg/ml medium) and incubated at 37 degrees Centigradefor additional 1 hour, such that the cells were pelleted and [³H] GS-HNEtransport was measured as described above. The values in FIG. 3 areshown as means.+−.S.D. (n=3 separate experiments) and * indicatesstatistically significant differences between treated and control cellsevaluated by the Student's t test (P<0.05).

To confirm that RalBP1 does indeed transport the GS-HFNE and not itsdegradation products or metabolites, the transported allocrite,hemiacetal of 3-(4-hydroxynonanyl) glutathione, was isolated from mediaand characterized by mass spectral analysis.

Increased efflux of GS-HNE was blocked by coating the cells withantibodies against RalBP1, confirming that GS-HNE was transported byRalBP1. More importantly, stress pre-conditioned cells with inducedhGST5.8 and RalBP1 acquired resistance to H₂O₂-mediated cytotoxicity(FIG. 4A) and to apoptosis by (FIG. 4B) suppressing a sustainedactivation of c-Jun N-terminal kinase and caspase 3. For FIG. 4A,aliquots (about 40 μL) containing 2×10⁴ control or heat shock treatedcells were washed with PBS and plated into 8 replicate wells in a96-well plate, wherein H₂O₂ (about 50 uM) in 10 μL of PBS was added andthe plates were incubated at 37 degrees Centigrade for 2 hours, afterwhich about 200 μL of growth medium was added to each well. Following 72hours of incubation at 37 degrees Centigrade, the MITT assay wasperformed and the OD₅₉₀ values of sample subtracted from those ofrespective blanks (no cells) were normalized with control values (noH₂O₂). Averages and standard deviations from three separatedeterminations of cytotoxicity of 4-HNE and H202 are shown in FIG. 4A.For FIG. 4B, 2.5×10⁶ K562 cells in 5 mL medium were treated with heatshock at 42 degrees Centigrade for 30 minutes, or 50 μM H₂O₂ (finalconcentration in medium) for 20 minutes and allowed to recover for about2 hours in normal growth medium at 37 degrees Centigrade. The cells,pre-conditioned with heat shock or H202 treatment, were treated withheat for 2 hours and 100 μM H₂O₂ for 2 hours. DNA (about 1 μg) extractedfrom the cells was electrophoresed on 2% agarose gels containing 10μg/mL ethidium bromide; lanes representing different treatments aremarked.

The protective effect of stress pre-conditioning against H₂O₂ or 4-HNEinduced apoptosis was abrogated by coating the cells with anti-RalBP1IgG, which inhibited the efflux of GS-HNE from cells (FIG. 5). For FIG.5, aliquots (about 50-100 μL) containing 1-2×10⁶ cells were fixed ontopoly-L-lysine-coated slides by cytospin at 500×g for 5 minutes and theTUNEL apoptosis assay was performed. Slides were analyzed byfluorescence microscope using a standard fluorescein filter andphotomicrographs at 400× magnification are presented. Apoptotic cellsshowed characteristic green fluorescence. FIG. 5 includes the following:Panel 1, control cells, without heat shock pre-treatment, incubated with20 μM 4-HNE for 2 hours; Panel 2, control K562 cells pre-treated withheat shock (42 degrees Centigrade, 30 minutes) and allowed to recoverfor 2 hours at 37 degrees Centigrade; Panel 3, cell pretreated with heatshock, allowed to recover for 2 hours at 37 degrees Centigrade followedby incubation in medium containing 2 μM 4-HNE for 2 hours at 37 degreesCentigrade; Panel 4, heat shock pre-treated cells, allowed to recoverfor 1 hour at 37 degrees Centigrade, anti-RalBP1 IgG was added to medium(20 μg/mL final concentration) and incubated for an additional 1 hourand cells were then incubated for 2 hour at 37 degrees Centigrade inmedium containing 20 μM 4-HNE.

Induction of hGST5.8 and RalBP1 by mild, transient stress and theresulting resistance of stress-pre-conditioned cell to apoptosis is ageneral phenomenon, because it is not limited to K562 cells, but isevident in other cells (e.g., lung cancer cells, H69, H226, humanleukemia cells, HL60, human retinal pigmented epithelial cells) (datanot shown). Hence, transport activity of RalBP1 regulates theintracellular levels of potential toxic by-products. Examples of toxicby-products are the lipid peroxidation products involved in apoptosissignaling, differentiation, and cell proliferation.

Radiation Protection with RalBP1

The protective effects of RalBP1 goes beyond its protection ofpotentially toxic chemical substituents and their by-products.RalBP1-enriched cells are also resistant to toxicity from radiation. Forexample, as shown in FIG. 6, cells enriched with RalBP1 are remarkablyresistant to radiation as compared to non-enriched control cells. Here,small cell lung cancer cells (H82) were loaded with RalBP1 by incubatingwith RalBP1 encapsulated in artificial liposomes. They were irradiatedat 500 cGy with high-energy photon (6×10 volt photon/min) for 1.25minutes. Cells were serially passaged daily by inoculating 0.5×10⁷trypan blue dye excluding cells/mL in fresh RPMI medium. For analysis,the cell density measured each day was normalized to cell density inrespective non-irradiated controls.

As such, electrophilic products of lipid peroxidase (LPO) caused byreactive oxygen species generated during radiation may partly accountfor cell killings by radiation. Clearly RalBP1-mediated transport ofGSH-conjugates of these electrophiles provides protection fromradiation. Such protection may be readily transferred to a larger scaleto protect mammals against damaging radiation, including ionizing,electromagnetic, thermal, and laser, wherein either long- or short-rangeelectrons are involved.

Therefore, RalBP1 mediates transport of endogenously generatedchemicals, metabolic products, their by-products and exogenouslyadministered drugs or radiation, and their byproducts. RalBP1 mediatesthe transport of most chemicals and by-products that also involve GS-E(e.g. conjugate of 4-HNE). For example, RalBP1-enriched cells areresistant to toxicity in the form of chemical toxicity (organic orinorganic) or from damage (e.g., from stress, oxidation, alkylation,radiation). The function of RalBP1 via an ATP-dependent efflux ofxenobiotics (e.g., GS-E and exogenous and endogenous electrophiles) isshown in FIG. 7. Here, xenobiotics, radiation, their metabolites,mitochondrial electron transport and metal ions generate reactive oxygenspecies (ROS) that can cause membrane lipid peroxidation and4-hydroxynonenal—the toxic end product of lipid peroxidation—cause DNAdamage leading to mutagenesis, carcinogenesis and apoptosis as well asmodulates the stress mediated signaling pathways. Clearly, RalBP1mediates the ATP-dependent efflux of a wide variety of metabolic,stress, and pharmaceutical by-products, such as amphiphilic drugs,GSH-conjugates (GS-E) of both xeno- and endo-biotics, GS-HNE andleukotrienes, from eukaryotic cells. The transport of GS-E is crucialfor maintaining functionality of GSTs and glutathione reductase (GR),because these enzymes are inhibited by GS-E. RalBP1 regulates theintracellular concentrations of 4-HNE by a coordinated mechanism withcellular GSTs.

RalBP1 and Multi-Drug Resistance

RalBP1 is also involved in the mechanism of multidrug resistance ofcancer cells. RalBP1 mediates ATP-dependent primary active transport ofnot only anionic compounds (e.g., GSH-conjugates), but also the cationicchemotherapeutic drugs such as DOX, daunomycin and colchicine. Theprotein sequence of RalBP1 is not homologous to ABC-transporters—theproteins thought to be involved in the mechanisms of multi-drugresistance. RalBP1 (1) lacks any close homologs in humans; (2) displaysubiquitous expression in tissues; (3) lacks the classic nucleotidebinding Walker domains; (4) has integral membrane association withoutclearly defined transmembrane domains; and most importantly, (5) hasdistinct functions not present in other transporters (e.g., has a roleas a direct link to Ras/Ral/Rho and EGF-R signaling through itsmultifunctional nature including GAP-activity and Ras/Ral/Rho-regulatedeffector function involved in receptor mediated endocytosis). Itsmultifunctional nature is likely due to the presence of multiple motifsincluding Rho/Rac-GAP-domain, Ral-effector domain binding motif, twodistinct ATP-binding domains, H⁺-ATPase domain, PKC and tyrosine kinasephosphorylation sites, and its proteolytic processing into multiplesmaller peptides that participate as components of macromolecularfunctional complexes.

RalBP1 overexpression confers resistance to both DOX and alkylatingtoxins such as 4-HNE by increasing their efflux from cells. RalBP1 canalso modulate stress signaling by regulating intracellularconcentrations of 4-HNE, as it is involved in stress signaling.Antibodies against RalBP1 can block the transport of drugs and enhancecytotoxicity of these drugs (e.g., chemotherapeutic agents) to cancercells. The higher resistance to DOX of non-small cell lung cancer(NSCLC) cells as compared to the small cell lung cancer (SCLC) cellscorrelates with a higher RalBP1-mediated efflux of DOX in NSCLC. [SeeAwasthi S, et al. 2001. In Pharmacology and therapeutics in the newmillennium (Gupta, S. K., ed.), pp. 713-725, Narosa Publishing House,New-Delhi, India, incorporated herein by reference.] Coating with RalBP1antibodies sensitizes NSCLC to DOX by blocking their RalBP1 mediatedtransport. Taken together, the present invention demonstrates thatRalBP1 modulates drug sensitivity of cancer cells. RalBP1 is expressedin all human tissues and cell lines examined so far, and it catalyzesthe transmembrane movement of physiologically relevant ligands as wellas a wide variety of xenobiotics irrespective of their net charge.

The significance of RalBP1-mediated transport to the mechanisms ofmultidrug resistance may go beyond the protection of cells through drugefflux. RalBP1 also impacts on signaling mechanisms via the modulationof the intracellular concentration of GS-HNE and its precursor, 4-HNE,which is known to cause cell cycle arrest and promote differentiationand apoptosis in cancer cell lines (Cheng J Z, et al. 1999. Arch BiochemBiophys. 372:29-36; incorporated herein by reference). In addition, theeffects of 4-HNE on cell cycle signaling may be concentration dependentas it can have the opposite effect at lower concentrations whereproliferation is observed in the presence of low 4-HNE levels. The levelof 4-HNE reflects the stress status of the cell, and to convey thecorresponding signal to the cell cycle and/or apoptosis machinery.Induction of RalBP1, by damage, oxidative or chemical stress (e.g., dueto anticancer drugs), depletes 4-HNE and thus promotes the proliferationof cancer cells.

RalBP1 therefore has a two-pronged effect in multi-drug resistance; inaddition to xenobiotic and other potentially toxic chemical or drugtransport, RalBP1 shifts the signaling balance in favor of cellproliferation.

RalBP1 and Radiation Sensitivity Using Knockout Mice

As described, RalBP1 (also referred to as RALBP1 or Ral-binding protein)is a glutathione-conjugate transporter that is a critical component ofstress-response in cultured cells and provides protection from stressorsincluding heat, oxidant chemicals, chemotherapeutic agents, UVirradiation and X-irradiation.

C57B mice which carry heterozygous (+/−) or homozygous (−/−) deletion ofthe RIP1 gene (mouse version of RalBP1) were created. These mice werecreated using Cre-Lox technology that can selectively suppress genes(FIGS. 8A and B). From RIP1+/− animals, obtained from Lexicon Genetics,we established colonies of RIP1+/+, RIP1.+−., and RIP1−/− C57B mice bysegregation and mating of animals based on genotyping by polymerasechain reaction (PCR) on tail tissue (FIG. 8C). Western-blot analysis ofmouse tissues using anti RalBP1 antibodies confirmed decreased RIP1levels in the RIP1+/− mouse, and its absence in tissues from the RIP1−/−mouse (FIG. 8D).

For FIG. 8, the knockout and genotyping strategy is the following. Thesequence around the insertion site with the up and down-stream PCRprimers (in bold-underline) are shown (FIG. 8A; SEQ ID NO:3). The thirdprimer was an LTR primer (FIG. 8B; SEQ ID NO:4). About ten weeks old C57mice born of heterozygous×heterozygous mating were genotyped by PCRstrategy, in which mouse tail DNA was isolated and used as a template inPCR reaction. A sample genotyping result is given. When all threeprimers are used in PCR, DNA from wild-type animal should yield a 200 byband, knockout homozygous animal should yield a 150 bp band, andknockout heterozygous animal should yield both bands. In FIG. 8C, lane Mis DNA ladder, lanes 1, 2 and 3 are from homozygous knockout,heterozygous knockout and wild-type animals. FIG. 8D shows analysis ofRalBP1 protein in tissues from wild-type and RalBP1 knockout mice byWestern blot. Crude membrane fractions from several tissues wereprepared and subjected to SDS-PAGE with application of 100 μg proteinper lane. Gels were transblotted on to nitrocellulose membranes,followed by Western blotting using anti-RalBP1 IgG as primary antibody.The blots were developed with 4-chloro-1-naphthol as chromogenicsubstrate. Lane 1 contained detergent extract of bacterial membranesfrom rec-E. coli expressing RalBP1 (pET-30a[+]-RLQLIP-BL21(DE3)-). Lane2 was blank. Lanes 3-5 contained membrane extract from liver and lanes6-8 from heart. Lanes 3 and 6 contained protein from wild-type animal,lanes 4 and 7 contained protein from heterozygous RalBP1 knockoutanimal, and lane 5 and 8 contained protein from homozygous RalBP1knockout animals (FIG. 8D). β-actin expression was used as internalcontrol.

The present invention shows that loss of RalBP1 (shown as a RIP1knockout) will confer sensitivity to X-irradiation, radiationsensitivity of RIP1−/− mice was compared with the RIP1+/+ byadministering 500 cGy whole-body X-irradiation using a Varian ClinacLinear accelerator (2100C), followed by monitoring for survival. Arepresentative experiment (FIG. 9A) shows a dramatic 11 day differencein median survival between RIP1−/− (0/6 surviving by day 13) as comparedwith RIP+/+(2/6 surviving at day 28). These findings provide dramaticevidence for the radiation sensitivity conferred by loss of RIP1. ForFIG. 9, C57 RIP1+/+ (square) and −/− mice (diamond) were treated with500 cGy total body X-irradiation and survival was monitored. Each grouphad 6 animals (A). Western blot analyses of RIP1−/− mouse tissues wereperformed after i.p. injection of RalBP1-liposomes (B). In the upperpanel, RIP1−/− mice were treated with RalBP1-liposomes containing 200 μgRalBP1 protein i.p. and sacrificed 48 h later. In the lower panel,RALBP1−/− mice were treated with 3 doses of 200 μg RalBP1 liposomes attime 0, 72 h, and 120 h, followed by sacrifice at 168 h. Lanes labeled Care from mice treated with control liposomes without RalBP1 and Rdenotes mice treated with RalBP1-liposome. Tissues as indicated in thefigures were homogenized and aliquots of the detergent solubilized crudemembrane fraction containing 200 μg protein was subjected to SDS-PAGE,transblotted to nitrocellulose membrane using anti-RalBP1 as primaryantibody and peroxidase-conjugated goat-anti-rabbit IgG as secondaryantibody. The blots were developed with 4-chloro-1-napthol. β-actinexpression was used as loading control. RalBP1−/− mice treated witheither control liposomes (circle) or RalBP1-liposomes (+) at day −3, day+3 and day +5 of 500 cGy total body irradiation. Survival was monitored(C).

If loss of RIP I was the major determining factor in this acquiredradiation sensitivity, replacement of this deficit should reverseradiation resistance. Therefore, a liposomal delivery system forproviding recombinant human RalBP1 to the tissues of knockout animals ispresented. Methods for expressing recombinant human RalBP1 in E. coliand purifying the expressed protein to a high purity, >96% by amino acidcomposition analysis, and reconstituting its transport function inartificial liposomes are those commonly used by one of ordinary skill inthe art. [See Awasthi et al., Biochemistry 39, 9327 (2000); incorporatedherein by reference.] Liposomes were prepared in sufficient quantitiesand administered via the intraperitoneal (i.p.) injection to RIP 1−/−animals.

A single dose of RalBP1-liposomes containing 200 μg purified RalBP1administered i.p. followed 48 h later by sacrificing the animals andanalyzing tissues immunologically for presence of RalBP1 showedconvincingly that these liposomes could be used to deliver RalBP1 to alltissues of RIP1−/− mice (FIG. 9B). Administration of 3 doses ofRalBP1-liposomes at the same dose over 8 days followed by sacrifice atday 10 showed further accumulation of RalBP1 in the RIP1−/− mousetissues (FIG. 9C).

These Western-blot analyses confirmed the lack of any detectable RIP1 inany tissue from the −/− mouse and presence of a band at the expected Mwof 95 kDa for intact RalBP1 in all tissues examined from mice treatedwith RalBP1 liposomes. The 38 kDa band represents a C-terminalproteolytic fragment of RalBP1 beginning at aa 424. Remarkably, even thebrain tissue took up a significant amount of RalBP1, a finding that mayhave significant pharmacological implications for delivery of drugs tothe brain or other organs. The RalBP1 liposomes may incorporate one ormore genes and targeted markers in order to deliver the gene to thetargeted organ(s) of a mammal.

Delivery of RalBP1 to mouse tissues also results in reversal ofradiation sensitivity. The example used to show this is with 12 male RIP1−/− mice randomized into two groups of 6, the first group receivingcontrol liposomes containing no RalBP1, and the second group receivingRalBP1-liposomes administered by i.p. injection. Animals were subjectedto 500-cGy whole-body X-irradiation and followed for survival. Adramatic difference is survival was observed with all 6/6RalBP1-liposome treated animals surviving at 55 days, as compared with0/6 control-liposome treated animals surviving by 13 days postirradiation (FIG. 9D). Remarkably, the RIP 1−/− mice supplemented withRalBP1 had significantly improved survival as compared with even theRIP1+/+ mice. These finding conclusively demonstrate the radiationprotective effects of RalBP1.

The mechanism for this radioprotective effect of RALBP1 was investigatedin transport studies looking at the effect of RIP1 genomic deletion onGS-E transport capacity, oxidative-stress, and glutathione-linkedantioxidant enzymes in animals without or with radiation. For transportstudies, crude membrane inside-out vesicles (IOVs) from differenttissues were used. The reaction mixture consisted of IOVs protein, 10 mMTris-HCl, pH 7.4, 250 mM sucrose, 4 mM MgCl₂ and either 4 mM ATP or anequimolar concentration of NaCl. To start the reaction, appropriatevolume of radiolabeled ¹⁴C-DOX or ³H-DNP-SG was added. The uptake wasstopped by rapid filtration of the reaction mixture through 96 wellnitrocellulose plate (0.45 1 μm pore size). After filtration, thebottoms of the nitrocellulose membranes were blotted dry with filterpaper and punched out, and the associated radioactivity was measured byplacing in liquid scintillation fluid. ATP-dependent uptake of either¹⁴C-DOX or ³H-DNP-SG was determined by subtracting the radioactivity ofthe control without ATP from that of the experimental containing ATP andthe transport of DOX or DNP-SG was calculated in terms of pmoles/min/mgIOV protein. GSH levels and enzyme activities for GST, GPX, GR, G6PD andγGCS activities were determined in 28,000×g supernatants of 10%homogenate, and LOOH and TBARS were determined in whole crudehomogenates using well established methods known to those of ordinaryskill in the art.

Radioprotection

The example used to show the radioprotective effect is a study with a2×2×3 factorial design (radiation×gender×genotype) and three animals pergroup. Six groups of irradiated animals were treated with 500 cGy wholebody X-irradiation, and a remaining six groups were un-irradiated.Animals were sacrificed and autopsied at day 8 after irradiation. Seventissues (brain, heart, lung, liver, kidney, intestine and spleen) wereexamined for content of parameters of oxidative injury andglutathione-linked enzymes. GS-E and DOX transport was examined in crudemembrane vesicles prepared from plasma membrane fraction of hearttissues. Data was analyzed by ANOVA with one-way, two-way and three-wayinteractions between the three variables (gender, genotype, radiation)being compared.

Consistent with the observed function of RalBP1 as a transporter of GS-Eand DOX in cell culture studies, GS-E and DOX transport in membranevesicles was found to be decreased in a stepwise fashion from the RIP1+/+, to RIP 1.+−., to RIP 1−/− mice (FIG. 10). For FIG. 10, DOX andDNP-SG transport was measured as previously described in crude membranevesicles from mRALBP1+/+, +/− and −/− mice heart tissues (upper twopanels, where C, and R represent un-irradiated and irradiated animalsrespectively, and M and F are male and female animals, respectively).Fold-changes shown in the TABLE 3 represent changes in +/− or −/−animals with respect to the +/+ animals. The values in the bold-fontrepresent fold-change in the −/− animals as compared with the +/−animals. Blue font shows a decrease. All values presented weresignificant at p<0.01 by ANOVA.

A greater than 80% loss of total GS-E and DOX-transport activity wasseen in the RIP 1−/− mice. The differences in transport rates werestatistically significantly lower in the RIP1+/− mice as compared withRIP1+/+, and in the RIP1−/− mice as compared with either RIP1+/− orRIP1+/+ mice. These findings demonstrate that RIP1 is the predominantGS-E and DOX transporter in mouse tissues.

As such, loss of RIP1 results in increased ambient levels of oxidativestress in tissues. To demonstrate, levels of two well-accepted markersof tissue oxidative stress, LOOH and TBARS, were assessed. Theseparameters were measured in homogenates from 7 tissues of each of 3animals per group in all groups. The values obtained from the RIP1+/−and RIP1−/− mouse tissues were normalized to the corresponding valuesfrom RIP1+/+ mice to obtain fold differences. When analyzed in aggregatefor all tissues (TABLE 3), significant (p<0.01) increase in both LOOHand TBARS was observed for both male and female animals in the RIP 1+/−animals as compared with RIP 1+/+ animals, and fold increase was greaterin the RIP 1−/− as compared with the RIP 1+/+ animals. The increase seenin RIP 1−/− was significant when compared with either RIP1+/+ or RIP1+/−mice. These findings conclusively demonstrated that progressive loss ofRALBP1 results in progressive increase in tissue oxidative stress.

TABLE 3 Effect of RIP1 knockout on parameters reflecting oxidativestress Un-irradiated Irradiated (500 cGy) +/− (Fold) −/− (Fold) +/−(Fold) −/− (Fold) Parameter M F M F M F M F LOOH ↑ (1.32) ↑ (1.37) ↑(1.94) ↑ (2.02) ↑ (1.62) ↑ (1.63) ↑ (2.10) ↑ (2.22) ↑ (1.47) ↑ (1.48) ↑(1.60) ↑ (1.63) TBARS ↑ (1.18) ↑ (1.17) ↑ (1.68) ↑ (1.59) ↑ (1.43) ↑(1.42) ↑ (1.94) ↑ (1.83) ↑ (1.42) ↑ (1.35) ↑ (1.64) ↑ (1.56) GSH ↑(1.31) ↑ (1.48) ↑ (1.45) ↑ (1.59) ↑ (1.46) ↑ (1.58) ↑ (1.57) ↑ (1.76) ↑(1.10) ↑ (1.70) ↑ (1.20) ↑ (1.19) GST ↓ (0.84) ↓ (0.85) ↓ (0.81) ↓(0.82) — — — — — — — ↑ (1.11) GPX ↓ (0.64) ↓ (0.79) ↓ (0.54) ↓ (0.63) ↓(0.73) ↓ (0.88) ↓ (0.57) ↓ (0.70) ↓ (0.85) ↓ (0.81) ↓ (0.90) GR ↓ (0.82)↓ (0.84) ↓ (0.70) ↓ (0.77) — — ↓ (0.73) ↓ (0.76) ↓ (0.85) ↓ (0.91) ↓(0.89) ↓ (0.91) G6PD ↓ (0.82) ↓ (0.88) ↓ (0.78) ↓ (0.83) — ↑ (1.19) — ↑(1.17) — — ↑ (1.33) Γ-GCS — — — ↓ (0.79) — ↑ (1.14) — ↓ (0.91) — — —

For TABLE 3, methods for measurement of each parameter are those used byone of ordinary skill in the art. All parameters shown were measured intriplicate in brain, heart, lung, liver, kidney, intestine and spleenfrom each of 3 animals per group from 12 groups (3-genotype levels×2gender-levels×2 radiation levels). Radiation dose was 500 cGyadministered, and animals were sacrificed on day 8. The values forfold-changes between +/+vs. either +/− or −/− are shown in the lighterfont, and comparisons between +/− and −/− animals are in bold-fonts.Increases with respect to control are in red font and arrows (arrow-upbold), and decreases are in blue font and arrows (down arrow). Onlythose changes found to be significant by ANOVA (p<0.01) are presented,the missing values (−) were not significantly affected. Please seesupplemental tables for results of individual tissues for un-irradiated(see FIG. 11) and X-irradiated (see FIG. 12) animals, and results ofone- two- and three-way ANOVA for significant interactions betweengender, genotype and irradiation (See FIG. 13).

GSH, the chief soluble cellular thiol and chemical antioxidant, wasincreased overall, in contrast to the GSH-linked antioxidant enzymes,which were generally decreased. These findings suggest that RIP1 mayfunction, perhaps through regulation or Rho/Rac pathways, inup-regulation of these enzymes. Thus, increase in ambient LOOH could beexplained as a secondary effect of the loss of RIP 1 due to decreasedactivities of GST, GPX, GR and G6PD, which normally metabolize LOOH andconsume GSH. Increased GSH levels observed would thus be secondary todecreased consumption of GSH rather than increased synthesis, since therate limiting enzyme for GSH-synthesis, γ-GCS, was unchanged ordecreased. Analyses of these parameters by individual tissues supportedthis assertion (FIG. 11). The only tissue in which GSH, LOOH and TBARSwere decreased was liver, where GST and GPX were increased. Changes inoxidative stress parameters and antioxidant enzymes were generallyconcordant for most tissues for any given parameter, and the degree ofchange was generally greater in the RIP1−/− animals as compared with theRIP1+/− animals. Taken together, these findings confirm our hypothesisthat loss of RALBP1 results in global increase in tissue oxidativestress and changes in levels of GSH-linked antioxidant enzymes.

X-irradiation resulted in increase tissue oxidative stress withgenerally increased LOOH and TBARS in most tissues, and a greater degreeof increase in RIP1−/− as compared with the RIP1+/− animals (FIG. 12).TBARS levels were, however, actually somewhat decreased in liver. Withfew exceptions, radiation caused a further decrease in expression of theGSH-linked enzymes. These findings are likely a combined effect ofgender, genotype and irradiation which may affect the overall levels ofthese enzymes by causing varying levels of tissue damage (see results ofANOVA for one-way, two-way, and 3-way interactions in FIG. 13).

Whole mouse genome gene expression array was used to compare the effectof RIP 1 knockout in heart tissue, an organ particularly severelyaffected in RIP1−/− animals. The microarray data was analyzed usingcommercially available software. The entire array of 34,560 genes wasthen filtered based on the criteria for stepwise up-regulation, whichstated that there must be at least a 2 fold up-regulation on a givengene in the RIP1−/− mouse as compared with the RIP1+/+ mouse, and thatthe fold up-regulation between RIP1+/+ and RIP1.+−. mouse multiplied bythe fold up-regulation between the RIP1+/− and RIP1−/− mouse should bewithin 20% of that observed between RIP1+/+ and RIP1−/− mouse. Thiscriteria was chosen on the basis of results with GSH-linked enzymes inwhich step-wise up or down-regulation of each enzyme between RIP1+/+ andRIP1+/− mouse multiplied by that between the RIP1+/− and RIP1−/− mousewas roughly equal to the change between RIP1+/+ and RIP1−/− mouse. Ofthe 7 genes which satisfied these criteria (TABLE 4), four werestress-induced or heat-shock induced proteins.

For TABLE 4, a murine genome array was used to compare RIP1+/+ vs.RIP1+/−, RIP1+/+ vs. RIP1−/−, and RIP1+/− vs. RIP1−/−, each in duplicateand analyzed using IOBION software. Significant effects were selected bystipulating >2 fold increase, and by stipulating stepwise effectsdefined such that the up-regulation fold between RIP 1+/+ vs. RIP 1−/−is within 20% of the product of the up-regulation folds of RIP1+/+ vs.RIP1+/− and RIP1+/− vs. RIP1−/−. The 7 up-regulated genes satisfyingthese criteria are presented.

TABLE 4 Genes up-regulated in heart tissue of RIP1 knockout (+/+) vs.(+/−) vs. (+/+) vs. Description (+/−) (−/−) (−/−) heat shock protein1.09 1.53 2 heat shock protein 1, alpha 1.38 1.36 2.19 heat shockprotein Hsp40 1.08 2.09 2.27 105-kDa heat shock protein 1.12 2.57 2.3525-kDa mammalian stress protein 1 1.41 1.54 2.21 Stress-inducedphosphoprotein 1 1.56 1.37 2.08 insulin-like growth factor binding 21.72 3.62 protein 5

Heat Shock (Stress) Proteins [Hsp] are a family of proteins that vary insize (10 kDa to 110 kDa) and perform two essential functions within thecell. At homeostasis Hsp can behave as ‘chaperones’ assisting properfolding of and proper compartmentalization of other proteins. Hsp canunfold and refold improperly folded proteins into the proper orientationor assist in targeting them for degradation. In a stress inducedenvironment (temperature, xenobiotics, radiation, viral, and oxidativeinjury) where a higher likely hood of denatured proteins can exist, Hspcan mediate by either re-naturing the protein, degrading the protein,protecting the protein from becoming denatured, or transporting it to acompartment where it can be degraded. All of these actions assist thecell in maintaining its integrity. It is known that many Hsp areregulated by Heat Shock Factor 1 (Hsf-1). Hsf-1 is a transcriptionfactor that forms a ternary complex with some of the Hsp (inactiveform). Upon stress, the Hsp is released and Hsf-1 is allowed to bind toDNA, which up-regulates and increases the Hsp production assisting inrelief from the impending stress. It was recently discovered that Hsf-1forms a complex with Ral Binding Protein 1. Upon stress, the RalSignaling Pathway is activated and RalBP1 is removed from the complex,which allows Hsf-1 to translocate into the nucleus where it up-regulatedthe production of stress proteins. Thus, RalBP1 binding to Hsf-1 servesto inhibit Hsf-1 from increasing heat-shock protein RNA transcription.Our results are consistent with this postulate since loss of RIP1 causeda stepwise up-regulation of heat shock proteins.

The present invention demonstrates stress-resistance mechanisms and therole of GS-E transport in these mechanisms. The stress-defense functionsof RalBP1 have been strongly implicated in cell culture studies whichshow that it is induced within minutes of exposure to a variety ofstressors including radiant energy and oxidants, and serves to decreaseintracellular accumulation of GS-E. The formation of toxic andpro-apoptotic α,β-unsaturated aldehydes is an obligate result ofmembrane lipid peroxidation which is known to occur in response toradiant and oxidative stress. GSTs catalyze the reversible conjugationof these aldehydes with GSH, and the resulting GS-E is potent inhibitorsof GSTs as well as GR. Thus, the removal of these conjugates throughfurther metabolism to mercapturic acids or transport from cells iscritical, not only to prevent inhibition of these important GSH-linkedoxidant defense enzymes, but also to prevent accumulation of the parentaldehydes that can arise from the reverse reaction favored byaccumulation of these GS-E.

As such, RalBP1 serves a critical function in regulating cellular levelsof these α,β-unsaturated aldehydes which are known not only to becapable of cross-linking and denaturing proteins through formation ofSchiff s bases and alkylation but also to be capable of triggeringapoptosis once critical concentrations are reached. Induction ofheat-shock proteins as a defense in the absence of RalBP1 is entirelyconsistent with the protein-denaturing effects of α,β-unsaturatedaldehydes. Since oxidative stress which results from hydroxyl-radicalformation and formation of down-stream products of oxidation areaccepted as chemical mechanisms for the toxic effects of radiant as wellas chemical injuries, the function of RalBP1 in regulation ofintracellular levels of these end-products of oxidation is entirelyconsistent with the proposed role of RalBP1 as a prominentradiation-defense.

The linkage of RalBP1 to the Ral and Ras pathways and in particular tothe Rho/Rac pathway, which is known to control stress responses, is alsoof fundamental significance and similar links have not been found forother transporters. Although clear evidence has been provided for theinteraction of RalBP1 with these pathways, mechanistic explanationsregarding how RalBP1 is involved in mediating a diverse array offunctions has previously been far from clear. Through itsprotein-protein binding motifs in the C-terminal domain, it has clearlybeen shown to bind important signaling proteins including the AP2clathrin adaptor protein, POB1, CDK1, and Hsp90 as well as Hsf-1.Therefore, these proteins may be regulating some effector function ofRalBP1. In addition, RalBP1 may be functioning as a regulator of thesesignaling proteins.

As described herein, RalBP1 has an effector function as an activenucleotidase which is capable of coupling ATPase activity withtrans-membrane movement of several allocrites. [See also, S. S. Singhalet al, Int J. Oncol. 22, 365 (2003); S. Awasthi et al., Biochemistry 39,9327 (2000); S. Awasthi et al., Biochemistry 40, 4159, (2001); S.Awasthi et al., Int. J. Oncol. 22, 713 (2003); S. Awasthi et al., Int.J. Oncol. 22, 721 (2003); S. Awasthi et al., J. Clin. Invest. 93, 958(1994); all citations herein incorporated by reference.] RalBP1 has aC-terminal domain of RalBP1 and is found both in membrane as well ascytosol, it contains an active ATPase domain. The present inventiondemonstrates that RalBP1 is a modular protein containing multipledomains which may perform distinct functions at distinct intracellularsites.

The dramatic effect of RalBP1 liposomes in providing complete protectionfrom radiation toxicity has direct implications for treatment ofradiation toxicity. The very real risks of radiation poisoning as aresult of a nuclear accident, nuclear bombs, or even terrorist attackswith “dirty-bombs,” mandate the critical need for post-exposuretreatment of radiation victims. As described herein, RalBP1 liposomesare excellent candidates for development as a radiation protective agentwhich may have broad applicability, particularly given that theseliposomes are capable of delivering sustained levels of RalBP1 in alltissue, even brain. These findings also indicate that these liposomesmay be useful as vehicles for delivery of drugs, antisense therapies andother therapies to the brain.

Thus, RalBP1 displays distinct transport properties as a nonselectivetransporter of neutral and charged compounds, is involved in multidrugresistance, and plays a role in modulating cellular signaling thataffects cell proliferation and cell death. As a proteoliposome, RalBP1may be provided to a mammal to protect against xenobiotic toxicity.Similarly, transfection of cells with an effective portion of RalBP1that enables transporter activity will promote xenobiotic protection,including protection from environmental or other chemicals (e.g.,stress-induced, drug delivered, physiologically induced). Protectionincludes the treatment, inhibition, reduction, or prevention ofaccumulation in one or more cells of any chemical, that, when degraded,has the potential to damage these cells. This protection may be forenvironmental purposes, chemical procedures, or for mammals in needthereof

The present invention is also a method of reducing the effects ofionizing radiation on one or more cells in an organism comprising thestep of contacting the organism with a liposome further comprisingRalBP1 or an effective portion of RalBP1.

Still another form of the present invention is a method of enhancing theexport of toxic compounds from mammalian cells comprising the step ofcontacting one or more mammalian cells with a liposome furthercomprising RalBP1 or an effective portion of RalBP1.

The present invention is also a method of transfecting mammalian cellsto enhance the transport of toxic compounds comprising the step ofcontacting the organism with a liposome further comprising RalBP1 or aneffective portion of RalBP1.

Another form of the present invention is a method of transfectingmammalian cells to enhance the resistance to ionizing radiationcomprising the step of contacting one or more mammalian cells with aliposome further comprising RalBP1 or an effective portion of RalBP1.

In still another form, the present invention is a method of enrichingmammalian cells to enhance their resistance to toxic compounds(including ionizing radiation) comprising the following step ofcontacting the organism with a liposome further comprising RalBP1 or aneffective portion of RalBP1.

In addition, the present invention is a proteoliposomal composition forthe treatment of toxic compound exposure comprising a liposome furthercomprising RalBP1 or an effective portion of RalBP1 and achemotherapeutic agent. Another form of the present invention is aproteoliposomal composition for the treatment of toxic compound exposurecomprising a liposome further comprising RalBP1 or an effective portionof RalBP1 and an effective dose of radiation therapy.

In yet another form, the present invention is a protein composition thatprotects one or more cells against the harmful accumulation of toxiccompounds comprising RalBP1 or an effective portion of RalBP1 and aligand to RalBP1 that enhances transport activity of RalBP1.

The present invention also embodies a kit for protecting one or morecells in an organism from the accumulation of one or more toxiccompounds comprising an effective dose of a liposome further comprisingRalBP1 or an effective portion of RalBP1 and an instructional pamphlet.

The present invention also includes a method of enhancing the resistanceof one or more mammalian cells to toxic compounds comprising the step ofcontacting one or more mammalian cells with a liposome furthercomprising RalBP1 or an effective portion of RalBP1.

While specific alternatives to steps of the invention have beendescribed herein, additional alternatives not specifically disclosed butknown in the art are intended to fall within the scope of the invention.Thus, it is understood that other applications of the present inventionwill be apparent to those skilled in the art upon reading the describedembodiment and after consideration of the appended claims and drawing.

What is claimed is:
 1. A method of reducing effects of radiationtoxicity in a subject exposed to radiation, the method comprising thesteps of selecting a subject with or at risk of developingradiation-induced toxicity and administering to the subject aproteoliposomal composition comprising a liposome and RLIP76 beforeand/or after the subject has been exposed to the radiation, whereinadministration reduces the effects of the radiation toxicity in thesubject.
 2. The method of claim 1, wherein the RLIP76 comprises two ATPbinding sites.
 3. The method of claim 1, wherein the RLIP76 comprisesamino acids 1-367 of SEQ ID NO:2.
 4. The method of claim 2, wherein theRLIP76 comprises amino acids 410-655 of SEQ ID NO:2.
 5. The method ofclaim 1, wherein the RLIP76 comprises the amino acid sequence GKKKGK. 6.The method of claim 1, wherein the RLIP76 comprises the amino acidsequence GGIKDLSK.
 7. The method of claim 1, wherein the RLIP76comprises amino acids 1-367 and 410-655 of SEQ ID NO:2.
 8. The method ofclaim 2, wherein the first ATP binding site is located in amino acids1-367 of SEQ ID NO:2 and the second ATP binding site is located in aminoacids 410-655 of SEQ ID NO:2.
 9. The method of claim 1, wherein theRLIP76 comprises a RLIP76 GTPase-activating domain and a Ral bindingdomain.
 10. The method of claim 1, wherein the liposome is selected fromthe group consisting of lectin, glycolipid, phospholipid andcombinations thereof.
 11. The method of claim 1, wherein the radiationis selected from the group consisting of therapeutic radiation, x-rayradiation, gamma radiation, ultraviolet radiation and nuclear radiation.12. The method of claim 1, wherein the radiation is therapeuticradiation.
 13. The method of claim 1, wherein the radiation is nuclearradiation.
 14. The method of claim 1, wherein the radiation isultraviolet radiation.
 15. The method of claim 1, wherein theproteoliposomal composition is administered to the subject 3 days prior,3 days after and 5 days after the radiation.
 16. The method of claim 1,wherein the proteoliposomal composition is administered to the subjectprior to radiation exposure.
 17. The method of claim 1, wherein theproteoliposomal composition is administered to the subject afterradiation exposure.
 18. The method of claim 1, wherein theproteoliposomal composition is administered to the subject prior to andafter radiation exposure.
 19. The method of claim 1, wherein theproteoliposomal composition is administered in one dose.
 20. The methodof claim 1, further comprising preparing the proteoliposomal compositionby contacting the liposome with RLIP76 or a portion thereof.